Question

Differentiate between humoral and cellular immunity. Include what cells they use and the steps they take to protect the body from infection. I want a detailed accounting of what happens when both types encounter an antigen

Answer 1

Humoral immunity and cell mediated immunity are 2 adaptive immunity in which a specific immune response occur against a particular pathogen.

In humoral immunity Antibodies are produced by the plasma B cells which cause immune response against Pathogens.Humoral Immunity (B cells)Kills pathogens with Extracellular Antigens

In cell mediated immunity, T cells induce the apoptosis(Cell Death) of the infected cells(Pathogens).Cell Mediated Immunit(T cells)Kills Viruses and Intracellular Pathogens

Humoral Immuntiy-

Humoral Immunity is mediated by macromolecules found in extracellular fluids (Blood) such as secreted antibodies, complement proteins etc. Since it involves substances found in body fluids(humors) it is named as Humoral Immunity.

Humoral Immunity Is also Called Antibody mediated Immunity.

Humoral Immune response is mediated by B cells. Each B cell have unique antibody which binds with a particular antigen.

when a pathoden encounter,The mature B cells migrate from the bone marrow to the lymph nodes or other lymphatic organs-----------The antigen is bound to the receptor and taken inside the B cell by endocytosis--------helper T cell to bind to the complex-----Helper T cells gets activated and release cytokines---------cytokines induce B cells to divide rapidl-------------- thousands of identical clones of the B cell are Formed----------They Forms plasma cells or memory cells.

memory cells: cells that remember the same pathogen and cause faster antibody production in 2nd infection by same pathogen

Plasma Cells:Antibody-secreting cell arising from B cell differentiation.

This Antibodies Cause destruction/Damage to the antigen by-

1.Neutralization

2.Agglutination

3.Precipitation

4.ACtivation of compliment system

Neutralization:process in which Antibodies coat extracellular pathogens and neutralize them by blocking key sites on the pathogen .

Agglutination:This is the clumping of cells such as bacteria or red blood cells

Precipitation: formation of lattices (cross-links) when Pathogens are soluble.

Activation of compliment system:Antibodies activates Compliment system that lyse the microbes that have entered into the host

Cellular Immunity-

This type of Immunity involves activation of phagocytes, cytotoxic T cells and the release of cytokines and chemokines in response to antigen.Here, CD4 cells or helper T cells provide protection against pathogens.

When antigen encounter antigen-presenting cells (APCs)---- immature T cells ----- converted into activated effector T cells  ( APCs----- macrophages, dendritic cells, and sometimes B cells).

Effector T cells can be 3 types-

1. Cytotoxic T cells------------ kill infected target cells by apoptosis.

2) TH1 cells---------- activate macrophages and Natural killer cells---Phagocytosis by Macrophages&secretion of cytotoxic granules (fby natural killer cells)

3) TH2 cells----------- stimulate B cells into producing antibodies.